Petersen, in U.S. Pat. No. 4,057,636, discloses compounds of the formula ##STR2## wherein R.sup.1 is straight or branched, saturated or unsaturated aliphatic hydrocarbon radical having from 1 to 8 carbon atoms, a cycloalkyl or cycloalkenyl radical having from 3 to 7 carbon atoms, an aryl or an aralkyl radical. These compounds are stated to be useful as antihypertensive agents. It has also been shown that those compounds are antihypertensive agents because of their potassium channel activating properties (I. Ahnfelt-Ronne and H. Jessen Jurgensen, Pinacidil (Pindac.RTM.): A New Antihypertensive Agent in Drugs of Today, Vol. 25, No. 1, p. 65-74 (1989)). Further, U.S. Ser. No. 230,209, filed Aug. 9, 1988, entitled "ARYL CYANOGUANIDINES: POTASSIUM CHANNEL ACTIVATORS AND METHOD OF MAKING SAME", discloses compounds of the formula ##STR3## wherein R.sub.1 is alkyl, alkenyl, alkynyl, haloalkyl, cycloalkyl, aryl, arylalkyl or cycloalkylalkyl to have potassium channel activating properties.